.a1{
    margin-left: 60px;
    width: 120px;
    height: 50px;
}
.a2{
    margin-left: 20px;
    width: 120px;
    height: 50px;
}
.a3{
    text-align: right;
    margin-left: 300px;
    width: 70px;
    height: 30px;
}
.a4{
    text-align: right;
    margin-left: 50px;
    width: 70px;
    height: 30px;
}
.a5{
    padding: 5px;  
    border: 1px solid #ccc;  
    border-radius: 4px; 
    margin-left: 0px;
    width: 400px;
    height: 40px;
}
.a6{
    position: relative;
    right: 2px;
    margin-left: 0px;
    width: 100px;
    height: 50px;
}
.a7{
    position: relative;
    left: 3px;
    top: 19px;
    margin-top: 100px;
    margin-left: 480px;
    width: 50px;
    height: 50px;
}
.a8{
    background-image: url('网页背景.png');
    background-size: contain;
}
.left{
    margin-top: 70px;
    margin-left: 125px;
    float: left;
    width: 15%;
}
.center{
    float: left;
    width: 55%;
}
.right{
    margin-top: 70px;
    float: left;
}
.b1{
    font-size: 180%;
    margin-left: 10px;
    margin-top: 20px;
}
.b2{
    font-size: 125%;
    margin-top: 40px;
    margin-left: 30px;
}
.b3{
    font-size: 125%;
}
ul li{
    margin-top: 7px;
}